Bonded Washers

bonded washers and dowty seals

  • Bonded Washer Seals are also known as Dowty Seals or Dowty Bonded Washers are high pressure seals typically used in the Mechanical, Hydraulic and Pneumatic applications.
  • Bonded Washer Seals were originally designed to replace copper type washers used in high-pressure systems. They consist of a metal washer and an elastomeric ring bonded inside the diameter. The metal washer prevents over-compression and limits deformation of the elastomeric ring.

 

 

Characteristics of Bonded Washer Seals

Ideal Pressure Gasket

Reliable sealing at high & low pressure

High & low temperature capability

Reduced bolt torque with no loss of tightening loads

Metal ring prevents over compression of the rubber seal

 

Properties and Description

Our bonded washers consist of a metal rectangular outer washer with a trapezoid shaped rubber ring bonded to the inner of the ring creating a 1-piece washer with an internal seal. Bonded washers hold a large amount of burst pressure whilst retaining the inner seal shape and limiting deformation resulting in brilliant sealing under high pressures.

EMI Seals & Gaskets Ltd can supply either the Standard style or a Self-Centering style that eliminates the potential of the being slightly seal offset during installation thus simplifying the process. These seals are readily available in Imperial sizes from 1/8 inch to 3 inches. French and German Metric form part of our extensive stock.  Imperial and metric size charts can be found at the top of our data sheets below. The inner bonded rubber seal can be manufactured to suit the end user’s application from the following:

 

EMI Material ReferenceElastomer NameStandard Elastomer Hardness Shore A
301Silicone (VMQ)75°±5 SHORE HARDNESS
302Fluorosilicone (FVMQ)75°±5 SHORE HARDNESS
309Nitrile (NBR)85°±5 SHORE HARDNESS
309-2Hydrogenated Nitrile (HNBR)80°±3 SHORE HARDNESS
303Fluorocarbon (FKM)75°±5 SHORE HARDNESS
306EPDM (EPDM)85°±5 SHORE HARDNESS
Other custom shore hardness’s are available depending on order quantity

 

Bonded Washer Thermal Properties

The thermal properties of the bonded washer seals will depend on the specific grade of compound used, please consult compound data sheets or contact a member of our Technical or Relationship Management Teams to discuss a potential project or application in greater detail.

Metal washer can be manufactured to suit the end user’s application from the following:

 

METALTENSILE STRENGTH MN/m2 (MINIMUM)SPECIFICATION
Mild Steel Pressings540BS 1449 Part 1 CS4 BRH5
Mild Steel Turned540BS 970 Part 1 EN8
Stainless Steel Pressings540BS 1449 Part 2 T316
Stainless Steel Turned540BS 970 Part 1 T303
Stainless Steel Turned540BS 970 Part 1 T316
Stainless Steel Turned540BS 970 Part 1 T304

 

Our Bonded Washer Seals are available with a variety of surface finishes:

 

SURFACE FINISHSPECIFICATION
Zinc platingDef. STAN. 03-20
Gold PassivateDef. STAN. 03-33
Cadmium PlatingDef. STAN. 03-19
Chromic AnodiseDef. STAN. 03-24/2
Sulphuric AnodiseDef. STAN. 03-25/2
Clear PassivateFe/Zn-5CIA
Zinc/Cobalt and Colour PassivateZnCb-921/ST140
Mechanical Zinc PlateSTD.5735,114 Fe/Zn 8 C1
Zinc/Iron and Black ChromateFe/Zn - Fe 5 C4
Sherardize 2000SHS 1091

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